Snap action electrical switch with adjustable differential action



Feb. 1, 1966 G. M. RUSSELL 3,233,055

SNAP ACTION ELECTRICAL SWITCH WITH ADJUSTABLE DIFFERENTIAL ACTION FiledApril 27, 1962 1; i7 15 12 INVENTOR:

United States Patent 3,233,055 SNAP ACTION ELECTRICAL SWITCH WITHADJUSTABLE DIFFERENTIAL ACTION Grover M. Russell, Goshen, Ind., assignorto Penn Controls, Inc, a corporation of Indiana Filed Apr. 27, 1962,Ser. No. 190,593 7 Claims. (Cl. 20067) The present invention relates topositive action switches and more particularly to a positive actionswitch wherein the switch is thrown to one position when the actuatingplunger is moved to a first position and is thrown to another positionwhen the actuating plunger moves to a second position different from thefirst position.

Positive action switches or snap switches as they are commonly known inthe art have been manufactured in a number of forms. Generally speaking,they consist of a flexible arm which is contacted by an actuatingplunger to force the flexible arm past an over center position. As soonas the flexible arm is forced past such an over center position theconstruction of the switch is such that the portion of the arm carryingelectric contacts will move from positive contact with a stationarycontact on one side of it to contact with a stationary contact on itsother side by a single positive movement known commonly in 'the art asthe snap action. A positive action switch of this type is disclosed inUS. Patent 2,789,173, issued April '16, 1957. When the plunger isretracted away from the flexible arm in such devices, the flexible armagain passes over its over center position which causes the flexible armto snap the contacts carried by it back to their first position. Thus abasic characteristic of these devices is that the switching action willoccur at substantially the same position of the plunger regardless ofwhether the plunger is traveling in one direction or the other for thereis only a very small distance of a few thousandths of an inch betweeneach side of the over c'enter position. Therefore, it is the practice atthe present time to utilize more than one positive action switchwhenever it is desirable to have switching in a circuit occur atdifferent positions of the device which actu'ates the switch plunger.The present invention overcomes this problem by providing means in asingle positive action switch for differential switching positions ofthe actuating plunger.

Thus it is an object of the present invention to provide a new andimproved positive action switch.

Another object is to provide a snap action switch wherein the" switchingaction in one direction occurs at a different position of the actuatingplunger than the switching action in the opposite direction.

' A further object is to provide adjustment means in a positive actionswitch of the type stated in the previous object for adjusting thedistance of its actuating plunger travel between switch operation in onedirection and switch operation in ,the opposite direction.

An additional object is to provide abutments connected to an actuatingplunger of a positive action switch of the aforementioned type whichwill cause the switch to operate in one'direction when engaged by oneabutment and will cause the switch to operate in the opposite directionwhen the switch arm is engaged by the other abutment wherein the spacingbetween the abutments determines the distance of plungers travel betweenswitching action in opposing directions.

Further objects and advantages will become apparent from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a top view of a portion of an embodiment of the presentinvention with a top cover removed;

FIG. 2 is a cross sectional view of the embodiment shown in FIG. 1 takenalong the line 2-2;

3,233fi Patented Feb. 1, 1966 FIG. 3 is a partial cross sectional viewof the embodiment as shown in FIG. 2 with some of the operational partsshown in a different position; and

FIG. 4 is a partial cross sectional view similar to FIG. 3 but withseveral of the operational parts positioned diiferently than shown inFIGS. 2 and 3.

While this invention is susceptible of embodiment in many differentforms, there is shown in the drawings and will herein be described indetail a preferred embodiment of the invention with the understandingthat the present disclosure is to be considered as an exemplification ofthe principle of the invention and is not intended to limit theinvention to the embodiment illustrated. The scope of the invention willbe pointed out in the appended claims.

It has been normal practice in the past to secure electrical contactsnear one end of a flexible arm in a positive action switch and to securethe other end of the arm to the base of the switch with an actuatingplunger slidably positioned to engage the flexible arm at some pointintermediate to the contacts and the secured other end. The movement ofthe plunger is usually opposed by a resilient device, often a springdevice, which impinges against the other side of the arm opposite theactuating plunger. Thus, when such a positive action switch is mountedin machinery or equipment so that the actuating plunger has its externalend engageable by an operating mechanism, the actuating plunger isforced inwardly until a point is reached at which switching operationoccurs in one direction. When the plunger is retracted, the switchingoperation in the opposite direction will occur substantially at the sameposition the plunger was in when the switching operation occurred in thefirst direction. There is a small variance usually present between theposition of a plunger for operation of a switch in one direction and foroperation in the other caused by the resilient characteristics of itsflexible arm and friction. However, this variation is of the order often thousandths of an inch or less. Further, the variation in length ofthis small distance is essentially uncontrollable.

At the present time, there are many applications for positive actionswitches wherein it is highly desirable to have the switching operationin one direction occur at one position of the actuating plunger and theswitching action in the opposite direction not occur until the actuatingplunger has been withdrawn to a position which is the order of thirtythousandths to one hundred and fifty thousandths of an inch further awayfrom the position of the plunger which causes switching operation in thefirst direction. Although this need is not new, no switch has beendevised prior to the present invention which will provide suchdifferential positions of the actuating plunger for operation of theswitch in opposing directions. The present invention provides not onlyfor accomplishing the opposing switching actions at differentialpositions of an actuating plunger but also provides means for adjustingthe distance between the differential positions of the actuatingplunger. Thus, my new positive action switch of which an embodiment willbe described in greater detail presently may be utilized in the same waya conventional positive action switch is utilized with substantially azero distance between the differential operating positions of theactuating plunger, or it may be set to provide for differentialswitching action with the distance between the differential actuatingpositions of the actuating plunger being adjustable.

Referring now to FIGS. 1 and 2, a snap action arm or blade 10, having aslot 11 therein of the type described in US. Patent 2,789,173, has oneend secured to a post 12 by a rivet 14. The post 12 is rigidly securedin a switch base 15. The switch base 15 may be constructed of plastic orother suitable material. A blade clamp 16 in the form of a U-shapedstrip of resilient material is secured to the base 15 by a screw 17. Thearms of the U-shaped strip 16 have V notches cut therein to receive theedges of the blade 10.

Rigidly secured in the base 15 are a pair of electrical posts 20 and 21to which are rigidly secured arms 22 and 23 by rivets 24 and 25,respectively. These posts and arms provide an electrical connection to apair of electrical contacts 26 and 2'7 which are secured to the arms 22and 23, respectively. The flexible arm has a pair of electrical contacts28 and 29 rigidly secured to it free end and positioned to contact thecontacts 26 and 27 alternately as the movable portion of the arm isswitched between its two static positions.

As shown in FIG. 2, a cover 30 encloses the top of the switch and iscemented in a recess 31 of the \base 15. An actuating plunger generallyindicated at 32 is slidably mounted in an aperture 33 of the cover 30.The actuating plunger 32 consists of a cylindrical portion 34 having aforked arm 35 extending therefrom, a plug 36 threaded into thecylindrical portion 34, and a pin 37 rigidly mounted in the .plug 36 bya press-fit so that the rotational adjustment of the plug 36 determinesthe protrusion of the pin 37 beyond a transverse semicircular abutment38 on the bottom of cylindrical portion 34. The transverse semicircularabutment 38 is shown by a dashed line in FIGURES 2, 3 and 4. A post 39is rigidly secured to the cover 30 to prevent the cylindrical portion 34from rotating in the aperture 33 by having the fork portion of the arm35 positioned so that the post 39 is within the fork.

An aperture 49 is provided in the blade 10 to allow the pin 37 to passtherethrough and engage an abutment 41 of a passive plunger 42 which isurged toward the blade 10 by a compression spring 43 placed between theplunger and the base in a bore 44.

Having described the general structure of the embodiment of the presentinvention illustrated in the drawings, the operation of this embodimentwill now be described in detail. FIG. 2 shows the cylindrical portion 34and the passive plunger 42 in the position which they assume when noforce is being applied to the external end of the cylindrical portion34. With the cylindrical portion in this position, the electricalcontact 28 is resting against the contact 26 to complete an electricalcircuit between the posts 12 and 20. The cylindrical portion 34 of theactuating plunger 32 is constructed of an electrical nonconductivematerial so that engagement of the pin 37 with the blade 11) will notcreate a short circuit if the external end of the plunger 32 should beengaged or grounded by structure external to the cover of the switch. Asis more fully described in U.S. Patent 2,789,173, tightening of thescrew 17 on the U-shaped blade clamp 16 will increase the stress on theblade 19 by forcing the arms of the clamp 16 to move closer togethercompressing the blade 16 therebetween. This action so stresses the blade1% that the two halves thereof on opposite sides of the slot 11 arebuckled upwardly. The degree of such buckling is adjusted by adjustingthe screw 17. When the blade 10 is stressed as just described, it willstay in either the elevated position of FIG. 2 or the depressed positionshown in FIG. 3.

As the actuating plunger 32 is forced downwardly to the position shownin FIG. 3, the abutment 38 will contact the upper surface of the blade10 forcing it downwardly until that portion of the blade in contact withthe abutment 38 forces the entire blade to snap to the depressedposition. When this occurs, the free end of blade 10 will swing contact28 away from contact 26 and bring contact 23 into engagement withcontact 27 so that the circuit from post 12 to post is broken and acircuit is completed between post 12 and post 21. The position of theactuating plunger 32 in FIG. 3 represents the position at which thedownward switching action of the blade 10 has just been accomplished.

FIG. 4 illustrates the position of the actuating plunger 32 and thepassive plunger 42 just prior to the occurrence of a switching actionwhich will bring blade 10 to its elevated position shown in FIG. 2.Thus, between the time that switching has occurred, as illustrated inFIG. 3, and the upward motion of the actuating plunger 32 to theposition illustrated in FIG. 4, no switching action has occurred and theplunger has moved upwardly approximately one hundred-thousandth of aninch.

During the time that the actuating plunger 32 was moving downwardly, thepin 37 was forcing the passive plunger 42 downwardly and thus carryingabutment 41 away from the lower side of the blade 10. As the actuatingplunge-r moves upwardly, the abutment 38 moves away from the top of theblade while the abutment 41 on the passive plunger 42 approaches thelower side until it contacts it as illustrated in FIG. 4. The upwardforce on the passive plunger 42 is provided by the compression spring43. As soon as the abutment 41 has engaged the lower side of the blade10 and has forced it to bulge upwardly until the blade 10 snaps to itselevated position, the contacts 27 and 29 will be disengaged from eachother and the contacts 26 and 28 will be re-engaged as shown in FIG. 2.When the actuating plunger 32 is forced downwardly again, it must movethe same approximately one hundred-thousandth of an inch while abutment41 is being forced away from the under side of the blade and abutment 38is being brought downwardly to contact the top side of the blade. Thus,it is read ly Seen that a differential is provided in the actuatingpositions of the actuating plunger for switch actuation in opposingdirections.

This differential distance between the actuation positions is easilyadjusted by rotating the threaded plug 36 with a screwdriver. Suchadjustment varies the amount of pin protrusion by pin 37 beyond theabutment 38 and therefore controls the distance between the abutment 38and the abutment 41. Those skilled in the art will easily recognize thatthere are a number of mechanical forms that could be utilized toadjustably vary the distance between two abutments such as 38 and 41which are within the scope of the present invention. An adjustment rangewhich varies the distance between the abutments from thirty-thousandthsto one hundred and fifty-thousandths of an inch has been foundsatisfactory for most applications.

I claim:

1. In a snap action electrical switch,

movable contact mechanism having a contact carrying member mounted formovement between two switching positions,

said mechanism including a portion actuatable ,bi-directiona-lly througha certain distance along a certain path of travel and means biasing saidactuatable portion against such actuation under conditions where saidportion is actuated through a predetermined amount of said certaindistance and then being effective for causing such actuation for .theremainder of such certain distance causing a snap action of saidactuatable portion and snapping of said .contact carrying member betweensaid two switching positions,

and actuator mechanism for actuating said actuatable portion,

said actuator mechanism including a first abutment positioned forengaging said actuatable portion in a first one of said bi-directionsand a second abutment positioned for engaging said actuatable portion inthe other of said bi-directions,

said abutments being interconnected one to the other to maintain apredetermined distance apart extending along said path of travel formovement in spaced unison during such bi-directional actuation.

2. In a positive action switch having an arm pivotally secured to arigid structure and having a portion there of stressed to assume eitherof two static positions when no actuating force other than a forcerequired to produce the positive action is applied to the arm, thecombination of:

a first abutment engageable With the flexible arm to force said movableportion to one static position,

a second abutment engageable with the flexible arm to force said movableportion to the other static position, and

means connecting said abutments to cause each of said abutments to moveaway from the arm by a predetermined distance before the arm iscontacted by the other abutment, said flexible arm assuming one or theother static position when neither abutment is applying force to saidarm.

3. In a positive action switch having an arm pivotally secured to arigid structure and having a portion thereof stressed to assume eitherof two static positions when no actuating force other than a forcerequired to produce the positive action is applied to the arm, thecombination of:

a member slidable relative to said arm and said rigid structure,

a first abutment cooperatively acting with said member to force saidmovable portion to one static position when said member moves to a givenposition in one direction, and

a second abutment cooperatively acting with said member to force saidmovable portion to the other static position when said member moves inthe opposite direction by a predetermined distance, said flexible armassuming one or the other static position when neither abutment isapplying force to said arm.

4. In a positive action switch having an arm pivotally secured to arigid structure and having a portion thereof stressed to assume eitherof two static positions when no actuating force other than a forcerequired to produce the positive action is applied to the arm, thecombination of:

a first abutment engageable with said arm to force said movable portionto one static position,

a second abutment engageable with said arm to force said movable portionto the other static position, said flexible arm assuming one or theother static position when neither abutment is applying force to saidarm,

means interposed between said abutments to cause each of said abutmentsto move away from the arm by a predetermined distance before the arm iscontacted by the other abutment, and

adjustment means connected to said abutment connecting means to vary thepredetermined distance.

5. In a positive action switch having an arm pivotally secured to arigid structure and having a portion thereof stressed to assume eitherof two static positions when no actuating force other than a forcerequired to produce the positive action is applied to the arm, thecombination of:

a member slidable relative to said arm and said rigid structure,

a first abutment cooperatively acting with said member to force saidmovable portion to one static position when said member moves to a givenposition in one direction,

a second abutment cooperatively acting with said member to force saidmovable portion to the other static position when said member moves inthe opposite direction by a predetermined distance, said flexible armassuming one of the other static position when neither abutment isapplying force to said arm, and

adjustment means connected to at least one of said abutments and to saidmember to vary the predetermined distance.

6. A diflerential positive action switch comprising:

a rigid mounting structure,

a flexible arm having a portion secured to the mounting structure andhaving another portion stressed to assume either of two static positionswhen no actuating force other than a force required to produce thepositive action is applied to the arm, said movable portion carrying anelectrical contact,

a hole in said arm,

an electrical contact secured to said mounting structure to form anelectrical connection with said contact on said movable portion whensaid movable portion is at one of said static positions,

an actuating member slidably mounted in said structure to bear againstone side of said arm when it is forced toward said arm and having anextension portion passing freely through the hole in said arm,

a passive member slidably mounted in said structure to bear against theother side of said arm and said extension portion passing through saidarm, said flexible arm assuming one or the other static position whenneither member is applying a force to said arm, and

a spring connected between said structure and said passive member tourge said passive member toward said extension portion and said arm.

7. A differential positive action switch comprising:

a rigid mounting structure,

a flexible arm having a portion secured to the mounting structure andhaving another portion stressed to assume either of two static positionswhen no actuating force other than a force required to produce thepositive action is applied to the arm, said movable portion carrying anelectrical contact,

a hole in said arm,

an electrical contact secured to said mounting structure to form anelectrical connection with said con- 'tact on said movable portion whensaid movable portion is at one of said static positions,

an actuating member slidably mounted in said structure to bear againstone side of said arm when it is forced toward said arm,

an extension portion threaded into said actuating member and having aportion passing freely through the hole in said arm, said extensionbeing rotatably adjustable to vary its distance of extension beyond saidactuating member,

a passive member slidably mounted in said structure to bear against theother side of said arm and said extension portion passing through saidarm, said arm assuming one or the other static positions when neithermember is applying force to said arm, and

a spring mounted between said structure and said passive member to urgesaid passive member toward said extension portion and said arm.

References Cited by the Examiner UNITED STATES PATENTS 2,627,002 l/1953Alvarez 2O067 2,789,173 4/1957 Kaminky 20067 FOREIGN PATENTS 551,021 2/'1943 Great Britain.

315,715 8/1956 Switzerland.

KATHLEEN H. CLAFFY, Primary Examiner.

ROBERT K. SCHAEFER, Examiner.

1. IN A SNAP ACTION ELECTRICAL SWITCH, MOVABLE CONTACT MECHANISM HAVINGA CONTACT CARRYING MEMBER MOUNTED FOR MOVEMENT BETWEEN TWO SWITCHINGPOSITIONS, SAID MECHANISM INCLUDING A PORTION ACTUATABLEBI-DIRECTIONALLY THROUGH A CERTAIN DISTANCE ALONG A CERTAIN PATH OFTRAVEL AND MEANS BIASING SAID ACTUATABLE PORTION AGAINST SUCH ACTUATIONUNDER CONDITIONS WHERE SAID PORTION IS ACTUATED THROUGH A PREDETERMINEDAMOUNT OF SAID CERTAIN DISTANCE AND THEN BEING EFFECTIVE FOR CAUSINGSUCH ACTUATION FOR THE REMAINDER OF SUCH CERTAIN DISTANCE CAUSING A SNAPACTION OF SAID ACTUATABLE PORTION AND SNAPPING OF SAID CONTACT CARRYINGMEMBER BETWEEN SAID TWO SWITCHING POSITIONS,